Methods of making foundry cores and moulds



United States Patent 3,179,523 METHODS OF MAKING FOUNDRY CORES AND MOULDS Rolf Erhard Morn, Alfredshem, Sweden, assignor to M0 Och Domsio Aktiebolag, Ornsiroldsvik, Sweden, a corporation of Sweden N0 Drawing. Filed Nov. 15, 1961, Ser. No. 152,665 Claims priority, application Great Britain, Nov. 21, 1960, 40,003 60 2 Claims. (Cl. 106--38.35)

This invention relates to the production of sand cores and moulds for foundry purposes.

According to the invention said cores and moulds are formed with the aid of a binder for the sand comprising a magnesium or zinc oxysalt cement and an organic binder. Sand cores and moulds thus formed and their use in casting are also included within the scope of the invention.

The cement may be magnesium oxychloride cement. Magnesium oxide may be mixed with magnesium chloride and a suitable amount of water added, whereupon the mixture hardens due to the formation of magnesium oxychloride. A mixture of zinc oxide and zinc chloride hardens in a similar manner by forming zinc oxychloride and can also be used. Salts other than the chlorides, such as sulphates, phosphates, silicates and nitrates, can also be used. It is also possible to use the magnesium or zinc oxide together with a calcium salt, such as calcium carbonate.

The cement compounds may be added to the sand used for forming cores and moulds in amounts of 1 to 15%, based on the weight of the sand, preferably 2 to 8%, together with the necessary amount of water, generally 1 to 10% by weight, based on the sand. The cores and moulds formed from the mixture may be allowed to selfharden by the reaction explained above. Hardening may take place in air at room temperature, but may also be carried out at a higher temperature by baking in an oven. It is also possible, however, to accelerate the hardening by passing carbon dioxide through the core or mould,

Standard formulation:

Magnesium oxide (MgO 3,179,523 Patented Apr. 20, 1965 whereby part of the cement reacts to form magnesium or zinc carbonate. In the latter case the core or mould advantageously contains an organic base or salt thereof, e.g. triethanolamine, as an accelerator.

Whether or not carbon dioxide is used in the hardening, a very hard and strong core or mould is obtained, which, however, collapses readily after the casting is finished and thus easily removed from the castings.

As above mentioned, the binder also comprises an organic binder in an amount of 0.2 to 10% by weight, based on the sand. The organic binder, which serves to increase the green strength of the core, to provide better plasticity in the sand mix, to improve the collapsibility and to a certain extent to control the setting time, may be a Water-soluble cellulose derivative, such as ethylcellulose, methylcellulose, hydroxyethylcellulose, ethylhydroxyethylcellulose or carboxymethylcellulose, or another water-soluble polysaccharide or polysaccharide derivative, such as strach, alginic acid or dexlrin, sugar, molasses, sulphite waste liquor, a thermosetting or thermoplastic resin, such as a phenolic resin, a melamine resin, a urea formaldehyde resin, 2. furfural resin, a polyvinyl resin, an acrylic resin, or an oil binder.

The binder may also comprise other inorganic additives or binders, such as plaster of Paris, Portland cement, lime, water-glass or a clay.

Wetting agents may also be included in the mix to improve the distribution of the water.

The invention is illustrated by the following examples. In all these examples, the percentages indicated are based on the weight of the sand. The sand used in the examples was a pure silica sand having an average grain size of about 0.27 mm.

In the examples, the various ingredients listed were added to the sand and the resulting sand mix was mixed well, whereupon standard test cores were prepared and tested for green compressive strength (compressive strength immediately after preparation of the test core) and for compressive strength after hardening.

Example I '7 Magnesium Chloride (MgCl: 7H O): 3% Additive according to the following table: 0.5%

Water: 3%

The compressive strength is obtained after storing in air at a temp. of 20 C.

Green strength compressive strength, gJmmfi, after standing, hours Additive (in/mm. 4 8 12 16 20 24 48 1. 22 23 48 92 185 224 316 327 0. 62 19 46 163 236 305 360 0. 54 20 40 167 214 252 360 Melamine resin 0. 61 22 43 83 200 265 Urea formaldehyde resin, 100% 0. 58 19 40 81 149 166 214 296 Hydroxyethylcellulose, high viscosity- 1. 08 18 57 124 225 333 360 360 Oarboxymethylcellulose, medium viscosity 1. 26 22 43 60 97 127 138 169 Dextrose 0. 68 21 44 84 144 235 360 Beet sugar 0.70 19 50 96 150 191 223 351 No additive 0. 55 21 48 85 168 207 205 246 Standard formulation:

Magnesium oxide (MgO): 2% Magnesium chloride (MgCl 711 Example II Compressive strength, glmm.

Green Shatter h Additive strength, index, Kept in air at 20 0., hours at g./mm. percent 4 l 8 12 15 24 48 8 16 I 24 I 48 0. 43 31 0 18 54 77 92 146 16 53 79 104 EHEC 0.2% 0.73 69 15 27 43 83 108 147 250 30 66 98 117 HEC 0.2 0.50 54 14 27 48 84 120 190 274 27 63 88 100 Example III Standard formulation:

Magnesium oxide (MgO)- 3% Magnesium chloride (MgCln, 711 0): 3%

Water: 3 Additive: Ethyl-hydroxyethylcellulose (EHE C) or hydroxyethyl cellulose (HEC) Compressive strength, gJmm.

Green Shatter Additive strength, index, Kept in air at 20 0., hours fi g g./mm. percent 4 8 12 16 20 I 24 I 48 8 I 16 I 24 48 0.43 16 28 82 111 155 193 225 32 104 145 157 EHEC 0.2% 0.75 17 36 79 133 193 244 323 39 122 180 201 HEC 0.2% 0. 54 59 16 34 67 191 227 330 36 128 182 206 Example IV Standard formulation:

Magnesium oxide (MgO): 4% Mangesium sulphate (MgSO 31110): 3.4%

Water: 5%

Kerosene: 0.2%

Additive: Hydroxyethylceilulose (HEC) Compressive strength, gJmrn.

7 Green Shatter Additive strength, index, Kept in air at 20 0., hours Kept air-tight at 20 0., hours gJmm. percent 0. 60 44 36 67 132 173 25 31 78 103 HEO 0.2% 0.70 41 51 104 217 22 36 88 153 HEC 0.4% 0.78 38 46 80 169 262 22 37 104 177 Example V Example VII Standard formulation Standard formulation Magnesium oxide (MgO) :3% 7 Magnesium oxide (MgO) :4% Magnesium sulphate (MgSO1, 311 0) 1.2% Magnesium sulphate (MgSOa, SE 0) 1.2 0

Magnesium chloride (MgCle, 7H2O) 1.5% Hydroxyethylcellulose (HEC), high viscosity 0.4%

Kerosene: 0.2% Water: 3, 4, 5 and 6% resp.

time: 1 hour at C.

Magnesium chloride (MgCl2, 7H20) 1.5%

Kerosene: 0.2% Water 4 7 Additive: liiydroxyethylcellulose (HEC) 0, 0.2, 0.4 and Baking 0.6% resp Water addition Green compressive Baked compressive Green compressive compressiYe strength percent strength, gJmm. strength, -lm-m. percent Strength g g; gggg g 2 5 5 0. 90 281 o 63 78 293 O. 72 360 0. 81 344 0 97 350 o. 79 360 08 333 60 ple VI Example VIII Standard formulation Standard formulation Magnesium oxide (MgO) 2.5, 3.0, 3.5, 4.0 and 4.5% resp. Magnes um oxide (MgO) 4% Magnesium sulphate (Mg'SO4, 3H O) 1.2% Magnesium phosphate (MgHPOr, 3H O) 2% Magnesium chloride (MgClz, 7H20) 1.5% Kerosene: 0.2% Hydroxyethylcellulose (EEC), high viscosity: 0.4% Water: 5% k Kerosene 0.2% 6 Additive 0.5% ethyl-hydroxyethylcellulose (EHEC), Water: 0.5% hydroxyethylcellulose (HEC) resp. Baking time: 1 hour at 160 C.

Cfmpr essfige strenggl, MgO Green compressive Baked compressive a er Expos g stre gth, -lmm. strength, g./mm.2 Addltive f fi ggfi gpl ggz in at 20 V 70 I Q 81 55 2 hrs. 24 1115. 0.86 563 0 98 2 EHEC 1.22 20 134 0. 97 350 e a: a 75 Example IX Formulation:

Magnesium oxide (MgO) 4% Calcium carbonate (CaCO 2% Ethyl-hydroxyethylcellulose: 0.6%

Water: 4%

Green compressive strength, g./mm. 1.5

Compressive strength, g./mm. after exposing in air at C.: 4 hrs. 47 8 hrs. 98 12 hrs. 125 16 hrs. 146 20 hrs. 184 24 hrs. 200

Example X Formulation:

Magnesium oxide (MgO): 4% Calcium carbonate (CaCO;,): 2% Ethyl-hydroxyethylcellulose: 0.4% Melamine resin: 0.4% Water: 4%

Green compressive strength, g./mm. 1.31 Compressive strength, g./mm. after exposing in air at 20 C.:

4 hrs. 28 8 hrs. 56 12 hrs. 115 16 hrs. 144 20 hrs. 147 24 hrs. 163

Example XI Formulation:

Magnesium oxide (MgO): 4% Calcium carbonate (C210): 2% Magnesium sulphate (MgSO .BH O): 0.5% Hydroxyethylcellulose: 0.6% Water: 4%

Green compressive strength, g./mm. 1.39 Compressive strength, g./mm. after exposing in air at 20 C.:

4 hrs. 34 8 hrs. 49 12 hrs. 89 16 hrs. 122 20 hrs. 135 24 hrs. 166

Example XII Formulation:

Magnesium oxide (MgO): 3% Magnesium chloride (MgCl .7H O): 1.5% Calcium carbonate (CaCO 2% Ethyl-hydroxyethylcellulosez 0.4% Water: 4% 7 Green compressive strength, g./mm. 2.28 Compressive strength, g./mm. after exposing in air at 20 C.:

4 hrs. 100 8 hrs. 105 12 hrs. 154 16 hrs. L 198 20 hrs. 230 24 hrs. 262

Example XIII Formulation:

Magnesium oxide (MgO): 3%

Calcium carbonate (CaCO 2% Magnesium sulphate (MgSO .3H O): 1.2% Magnesium chloride (MgCl .7H O): 1.0% Hydroxyethylcellulose: 0.4%

Water: 4%

Green compressive strength, g./mm. 1.55 Compressive strength, g./mm. after exposing in air at 20 C.:

8 hrs. 121 12 hrs. 241 16 hrs. 360 20 hrs. 360 24 hrs. 360

Compressive strength, g./mm. after toring in the absence of air at 20 C.:

8 hrs. 70

16 hrs. 176

24 hrs. 227 Compressive strength, g./mm. after baking at 160 C. for /2 hr. 360

Example XIV Example XV A composition comprising 50 g. of magnesium chloride,

and g. of graphite in 500 mls. of water is used to treat cores or moulds prepared as in Example 1. A hard smooth surface is obtained.

Example XVI Cores and moulds prepared as in Example I are surface-coated with a composition comprising 500 mls. of Water, 50 g. of magnesium chloride, 50 g. of magnesium oxide, 100 g. of graphite and 2 gof ethyl-hydroxyethylcellulose to render the surface hard.

Example XVII A composition comprising 500 mls. of ethanol (96%), 50 g. of mangesium chloride, 50 g. of mangnesium oxide and 100 g. of graphite is suitable for coating cores and moulds to make the surface harder.

I claim:

1. A method of making foundard sand mold members, which comprises (1) preparing a mixture consisting essentially of sand an cement-forming components selected from the group consisting of zinc oxysalt cementforming compounds and magnesium oxysal't cement-forming compounds in an amount of 1 to 15%, based on the weight of the sand (2) water in an amount of 1 to 10%, based on the weight of the sand and (3) an organic binder selected from the group consisting of Water-soluble polysaccharides and Water-soluble polysaccharide derivatives in an amountof 0.2 to 10%, based on the weight of the sand, forming mold members from the resulting mixture and hardening said mold members.

2. A method as in claim 1, in which said. organic binder is selected from the group consisting of hydroxyethylcellulose and ethyl-hydroxyethylcellulose.

References Cited by theExamilner UNITED STATES PATENTS MICHAEL V. BRINDISI, Primary Examiner.

MARCUS U. LYONS, Examiner. 

1. A METHOD OF MAKING FOUNDARD SAND MOLD MEMBERS, WHICH COMPRISES (1) PREPARING A MIXTURE CONSISTING ESSENTIALLY OF SAND AN CEMENT-FORMING COMPONENTS SELECTED FROM THE GROUP CONSISTING OF ZINC OXYSALT CEMENTFORMING COMPOUNDS AND MAGNESIUM OXYSALT CEMENT-FORMING COMPOUNDS IN AN AMOUNT OF 1 TO 15%, BASED ON THE WEIGHT OF THE SAND (2) WATER IN AN AMOUNT OF 1 TO 10%, BASED ON THE WEIGHT OF THE SAND AND (3) AN ORGANIC BINDER SELECTED FROM THE GROUP CONSISTING OF WATER-SOLUBLE POLYSACCHARIDES AND WATER-SOLUBLE POLYSACCHARIDE DERIVATIVES IN AN AMOUNT OF 0.2 TO 10%, BASED ON THE WEIGHT OF THE SAND, FORMING AND MOLD MEMBERS FROM THE RESULTING MIXTURE AND HARDENING SAID MOLD MEMBERS. 